The Benedictine monastery of St. Maria of Aquileia which nowadays houses the Museo Paleocristiano of Aquileia is one of the oldest and at the same time most significant church institutions of the Medieval "State" of the Patriarchs of Aquileia. Preserved written records reflect the special circumstances of this transition and contact zone, unique in Europe, where Roman, Germanic and Slavic traditions overlap. In comparison to previous research, the new findings in this edition - mainly concerning the period up to around 1200 - are primarily based on re-evaluations of documents and corrections of chronological approaches, as well as on a largely improved textual basis. On the other hand a considerable portion of the new material dating to the first half of the 13th century was previously entirely unknown. The edition is supplemented by descriptions of earlier research conducted on the monastery, the history of its tradition, the nature of legal transactions, property catalogues and the diplomatics of monastic documents. The volume contains an index of persons and locations and a word index (more specifically a phrase index) for quick and easy access.